BY2 consists of Singaporean twin sisters Miko (孫涵) and Yumi Bai (孫雨) who were born in Yio Chu Kang, Singapore on March 23, 1992— Miko is the eldest of the two while Yumi is the youngest. They are among the most internationally recognized Singaporean acts alongside the likes of JJ Lin and Stefanie Sun.
The twins had a passion for dance and music at a very young age, as they learned violin, piano, ballet, and many other styles of dancing such as Chinese traditional folk and ballet. As they grew older, they learned more modern forms of dance such as hip hop and street dance; their father was a driving force in nurturing the twins' career in music. However, he would pass away in 2007 before witnessing his daughters' debut and rise to stardom.
In 2007, they moved to Taiwan and joined Ocean Butterflies' Music Forest’s V Singer (“非常歌手”) training course at the age of 13 where they graduated with a “Best Costume Design” award and were granted a 10-year contract after being noticed by Billy Koh of Ocean Butterflies Music. Miko and Yumi were later sent to various countries in order to train and hone in their vocals and dancing skills.
Finally, in 2008, the sisters debuted their first album on July 25, with the studio album 16未成年 (NC 16) at the age of 16. The album peaked at number six on Taiwan’s G-Music chart from the 14th to the 25th.
In 2019, the girls announced that they had parted ways from Ocean Butterflies Music as their 10-year contract had ended. They established their own label By2 Studio. After the departure, the girls joined the Chinese singer’s program 明日之子 (The Coming One) in the “restart” category, auditioning with their very own track “DNA”, hoping to make a comeback in the Chinese music industry as their music career had been overshadowed by a variety of rumors from cosmetic surgery to dating (and cheating) rumors. When asked about why they had joined the show during their audition, Miko sated,
We’ve been waiting for this opportunity for three, four years now. Prior to this, it was the lowest period of our lives. I would say that… We’re facing a huge challenge in life now. [It feels] like the people that we loved and trusted had betrayed us, both in work and in love. It’s like we’re being abandoned. It’s actually really sad. We’ve always been here. It’s just that we couldn’t say or do anything.
The girls ended up ranking 3rd on the program and received a lot of praise from netizens, and later would release new music, such as 2020’s “異地戀人預告 (Long Distance Lovers)” and the COVID-19-inspired track “等你回家 (Wait For You to Come Home)”.
On top of music, the girls have also shown that they have been passionate about fashion, as they opened the fashion line DOUBLE TROUBLE in 2015 and Girl Gang Asia in 2017. The sisters also started an official YouTube Channel. Despite being highly active in Taiwan and East Asia, the sisters are now based in Los Angeles, California.